In UMTS (Universal Mobile Telecommunication System) that is one of the third generation mobile communication schemes (3G), HSDPA (High Speed Downlink Packet Access) is standardized as a method for realizing high speed packet transmission in a downlink from a base station to a mobile station.
In HSDPA, for increasing the throughput that can be realized, a packet scheduling technique is adopted in which users connected to the base station share radio resources and the base station preferentially assigns the radio resources to a user in a good propagation state.
In 3GPP (3rd Generation Partnership Project), a technique for choosing channels according to characteristics of a signal sent and received between the radio base station and the mobile station is adopted (refer to non-patent document 1, for example). For example, as to common control physical channel such as SCCPCH (Secondary Common Control Physical Channel), one channel is assigned to a plurality of mobile stations in a time division manner, and it is effective as a channel that can use radio resources efficiently among mobile stations.
On the other hand, in an uplink, a dedicated control channel assigned for each user while the mobile terminal is connected is used. FIG. 1 is a diagram showing an assignment example of the dedicated control channel. In FIG. 1, the lateral axis indicates time (t), and the vertical axis indicates frequency (f), and the frequency band is divided to a plurality of chunks.
In this example, as long as the user terminal UE1 is connected to the base station, a particular channel CH1 is assigned to the UE1. When the user terminal UE1 generates data at times t1 and t3, a necessary control signal is transmitted using the dedicated control channel CH1 according to the data generation. Also, a dedicated control channel CH2 is assigned to the user terminal UE2 during connection, data is generated at times t2 and t3, and a necessary control signal is transmitted using the dedicated control channel. At t3, although both of the user terminals UE1 and UE2 transmit an uplink control signal at a same time frame, collision does not occur since they use respective dedicated control channels.    [non-patent document 1] 3rd Generation Partnership Project; Technical specification Group Radio Access Network; UTRAN Iur interface user plane protocols for Common Transport Channel data streams (Release 1999)